Logic Puzzle

To determine how many sisters Sally has, let's carefully analyze the information provided:

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Step 1: Understand the family structure

• Sally is a girl.
• She has 3 brothers.
• Each brother has 2 sisters.

This means that from the perspective of each brother, there are 2 female siblings in the family — which includes Sally and one more sister.

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Step 2: Determine the total number of girls in the family

Since each brother has 2 sisters, and Sally is one of them, the other sister must be another girl in the family.

Thus, the family has 2 girls in total:

• Sally
• One other sister

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Step 3: Determine how many sisters Sally has

Sally is one of the two girls. Therefore, she has 1 sister (the other girl).

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Final Answer

$$ \boxed{1} $$